Littérature scientifique sur le sujet « Tunable telecom filters »

Optical filters have been adopted in many applications such as reconfigurable telecommunication switches, tunable lasers and spectral imaging. However, most of commercialized filters based on a micro-electrical-mechanical system (MEMS) only provide a minimum bandwidth of 25 GHz in telecom so far. In this work, the programmable filter based on a digital micromirror device (DMD) experimentally demonstrated a minimum bandwidth of 12.5 GHz in C-band that matched the grid width of the International Telecommunication Union (ITU) G.694.1 standard. It was capable of filtering multiple wavebands simultaneously and flexibly by remotely uploading binary holograms onto the DMD. The number of channels and the center wavelength could be adjusted independently, as well as the channel bandwidth and the output power. The center wavelength tuning resolution of this filter achieved 0.033 nm and the insertion loss was about 10 dB across the entire C-band. Since the DMD had a high power handling capability (25 KW/cm2) of around 200 times that of the liquid crystal on silicon (LCoS) chip, the DMD-based filters are expected to be applied in high power situations.

We design and evaluate the performance of a one-dimensional photonic crystal (PhC) optical filter that comprises the integration of alternating layers of a barium titanate ferroelectric (BaTiO3) and an yttrium oxide dielectric (Y2O3), with a critical high-temperature superconductor defect, yttrium–barium–copper oxide (YBa2Cu3O7−X), resulting in the (BTO/Y2O3)N/YBCO/(Y2O3/BTO)N multilayered nanostructure array. Here, we demonstrate that such a nanosystem allows for routing and switching optical signals at well-defined wavelengths, either in the visible or the near-infrared spectral regions—the latter as required in optical telecommunication channels. By tailoring the superconductor layer thickness, the multilayer period number N, the temperature and the direction of incident light, we provide a computational test-bed for the implementation of a PhC-optical filter that works for both wavelength-division multiplexing in the 300–800 nm region and for high-Q filtering in the 1300–1800 nm range. In particular, we show that the filter’s quality factor of resonances Q increases with the number of multilayers—it shows an exponential scaling with N (e.g., in the telecom C-band, Q≈470 for N=8). In the telecom region, the light transmission slightly shifts towards longer wavelengths with increasing temperature; this occurs at an average rate of 0.25 nm/K in the range from 20 to 80 K, for N=5 at normal incidence. This rate can be enhanced, and the filter can thus be used for temperature sensing in the NIR range. Moreover, the filter works at cryogenic temperature environments (e.g., in outer space conditions) and can be integrated into either photonic and optoelectronic circuits or in devices for the transmission of information.

We propose a novel semiconductor laser structure. It is composed of three cascaded active sections: a Fabry-Pérot laser section sandwiched between two gain-coupled distributed feedback (DFB) laser sections. We have modeled this multi-section structure. The simulation results show that compared with index- and gain-coupled DFB lasers, a significant reduction in the longitudinal spatial-hole burning can be obtained with the proposed device, and that this leads to a stable single longitudinal mode operation at relatively high optical power with a SMSR exceeding 56dB. Full Text: PDF ReferencesL.A. Coldren, "Monolithic tunable diode lasers", IEEE J. Select. Topics Quant. Electron. 6, 988 (2000) CrossRef O. Kjebon, R. Schatz, S. Lourdudoss, S. Nilsson, B. Stalnacke, L. Backbom, "30 GHz direct modulation bandwidth in detuned loaded InGaAsP DBR lasers at 1.55 [micro sign]m wavelength", Electron. Lett. 33(6), 488 (1997). CrossRef N. Kim, J. Shin, E. Sim, C.W. Lee, D.-S. Yee, M.Y. Jeon, Y. Jang, K.H. Park, "Monolithic dual-mode distributed feedback semiconductor laser for tunable continuous-wave terahertz generation", Opt. Expr. 17(16), 13851 (2009). CrossRef M.J. Wallace, R. ORreilly Meehan, R.R Enright, F. Bello, D. Mccloskey, B. Barabadi, E.N. Wang, J.F. Donegan, "Athermal operation of multi-section slotted tunable lasers", Opt. Expr. 25(13), 14426 (2017). CrossRef J.E. Carroll, J.E.A. Whiteaway, R.G.S. Plumb, "Distributed Feedback Semiconductor Lasers", Distributed feedback semiconductor lasers (IEE and SPIE, 1998). CrossRef H. Ghafour-Shiraz, Distributed Feedback Laser Diodes and Optical Tunable Filters (Wiley, 2003). CrossRef D.D. Marcenac, Ph.D dissertation (University of Cambridge, 1993). DirectLink L.M. Zhang, J.E. Carroll, C. Tsang, "Dynamic response of the gain-coupled DFB laser", IEEE J. Quant. Electr. 29, 1722 (1993). CrossRef W. Li, W.-P. Huang, X. Li, J. Hong, "Multiwavelength gain-coupled DFB laser cascade: design modeling and simulation", IEEE J. Quant. Electro. 36(10), 1110 (2000). CrossRef B.M. Mehdi, H. Rachid, in Proc. 3rd Intern. Conf. on Embedded Systems in Telecomm. and Instrument., Annaba, Algeria (2016). DirectLinkC. Henry, "Theory of the linewidth of semiconductor lasers", IEEE J.Quant. Electr. QE-18, 259 (1982). CrossRef K. Takaki, T. Kise, K. Maruyama, N. Yamanaka, M. Funabashi, A. Kasukawa, "Reduced linewidth re-broadening by suppressing longitudinal spatial hole burning in high-power 1.55-/spl mu/m continuous-wave distributed-feedback (CW-DFB) laser diodes", IEEE J. Quant. Electr. 39, 1060 (2003) CrossRef

The results of this Ph.D. thesis demonstrate the tunability of photonic platforms by introducing stimuli responsive polymers as constituents of the photonic structure itself or as thermally driven mechanical actuators. In particular, liquid crystalline networks (LCNs) were patterned by lithographic techniques, such as direct laser writing (DLW) and UV polymerization to develop and fabricate tunable photonic crystals for different applications, from tunable telecom filters to tunable structural colors and intelligent sensors, featuring good optical properties that can be controlled and modulated by multiple tuning mechanisms (e.g. temperature and light). In order to optimize the structure design and the tunability of LCN photonic devices, the refractive index and the tunable optical anisotropy (determined by the chemical composition of the material, the fabrication parameters, and the molecular ordering) have been precisely characterized. As first, it has been demonstrated, using a refractometer method, that optical properties of these new photonic materials can be tuned by adjusting mesogenic concentration both in LCN macro- and micro-structures. The tailored chemical formulation allows not only the determination of the shape changing properties of LCNs but also the modulation of the refractive indices and the optical anisotropy of liquid crystalline mixtures, which can be tuned at different temperatures or alternatively by laser light irradiation. Aiming to increase the fabricated structure resolution, a second result demonstrated how refined fabrication resolutions, never yet reached for liquid crystalline networks, can be achieved at low polymerization temperatures (5°C-10°C) using opportune writing parameters. The resulting 3D polymerizable unit, now comparable with the typical voxel of commercial resists, enlarges the application field of photo-responsive elastic materials without degradation of the patterned structure rigidity. Indeed, a spheroidal voxel would be the best polymerization unit to fabricate three-dimensional structures, especially in 3D photonic structures as woodpile photonic crystals for which isotropic voxel dimensions are needed. The best fabrication parameters using the DLW lithographic technique at controlled temperature enabled the fabrication of the first 3D woodpile photonic crystal made by LCN, having a geometric resolution and a light transmission attenuation at the stop band comparable with photonic crystal fabricated with commercial resists. This demonstrates the effectiveness of our previous study. Such photonic crystal has been characterized using temperature as an external stimulus to tune its optical properties in order to demonstrate its potential as a tunable filter at telecom wavelength. Finally, the first proof-of-concept of a smart millimetric optical sensor was developed during a six-month period in collaboration with Prof. Li and Prof. Keller group in Paris, at ChimieParis Tech. A temperature responsive actuator has been combined with the back side of the Morpho Menelaus wing, owing an optimized structural coloration due to its natural photonic crystal structure. Two different strategies have been proposed to control the visual sensor: a macroscopic deformation of the combined system induces an iridescence variation, whereas a nanoscale contraction generates a color shift through the lamellae interspacing variation, parameter that determines the structural coloration. In conclusion, this thesis focused on the material characterization of smart polymers and their nanopatterning for tunable photonic shows as the employ of smart LCNs can be extended from mechanical actuators and microrobotics to micrometric photonic structures for new multifunctional devices.

By exploiting the robust transport of light along the edges formed by two types of valley photonic crystals, we experimentally demonstrated a thermally tunable silicon topological photonic add-drop filter in the telecom band.